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921.
922.
以南京大胜关长江大桥为研究对象,建立其车桥耦合动力分析模型,采用逐步积分法求解动力方程,以动力系数作评判标准,讨论行车速度、阻尼比、行车方向、车辆数、吊杆布置方式等参数对动力性能的影响.结果表明:动力系数随行车速度的提高而增大;吊杆索力的动力系数与无应力索长成反比;随着阻尼比的增大,各构件动力系数均有所降低;同向行驶时... 相似文献
923.
综合国内外对铅芯橡胶支座力学性能的试验研究成果,考虑各种因素对支座水平方向恢复力模型的影响,提出了主要相关影响凶素的修正系数,依次对支座模型进行解耦分析.分析结果可以用来修止常用的铅芯橡胶支座恢复力模型. 相似文献
924.
925.
在深水桥墩及桩基础等结构地震反应中,地震激励下的水流动水压力对水中结构的作用以及结构位形变化对水体的反作用,属于典型的流固强界面耦合问题。以一顶端伸出水面的圆柱式结构为研究对象,基于任意拉格朗日-欧拉描述的Navier-stokes方程,建立了考虑水流-结构强耦合效应的水流-结构三维有限元模型。以正弦位移波输入,考察结构材料模量、水流流速和水位、激振频率和位移幅值等多种因素,分析了结构表面作用的动水压力反应特征以及水流动力效应,探讨了水流动力效应的主要影响因素。结果表明:考虑流固强耦合作用时,结构表面作用的动水压力及其分布具有强烈的频率依赖性,高频激励可显著增强动水压力作用;由于结构周围流体具有一定的粘滞性及动载作用下具有较强的辐射阻尼效应,水流动力效应对结构的位移、内力反应均有一定的抑制作用;激振频率、水流流速和水位以及结构材料模量等因素,对水流动力效应均有一定的影响。 相似文献
926.
In this paper, an explicit method is generalized from 1D and 2D models to a 3D model for numerical simulation of wave motion, and the corresponding recursion formulas are developed for 3D irregular grids. For uniform cubic grids, the approach used to establish stable formulas with 2M-order accuracy is discussed in detail, with M being a positive integer, and is illustrated by establishing second order (M=1) recursion formulas. The theoretical results presented in this paper are demonstrated through numerical testing. 相似文献
927.
Sean F. Gallen Karl W. Wegmann Kurt L. Frankel Stephen Hughes Robert Q. Lewis Nathan Lyons Paul Paris Kristen Ross Jennifer B. Bauer Anne C. Witt 《地球表面变化过程与地形》2011,36(9):1254-1267
The southern Appalachians represent a landscape characterized by locally high topographic relief, steep slopes, and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 Ma. The fundamental processes responsible for landscape evolution in a post‐orogenic landscape remain enigmatic. The non‐glaciated Cullasaja River basin of south‐western North Carolina, with uniform lithology, frequent debris flows, and the availability of high‐resolution airborne lidar DEMs, is an ideal natural setting to study landscape evolution in a post‐orogenic landscape through the lens of hillslope–channel coupling. This investigation is limited to channels with upslope contributing areas >2.7 km2, a conservative estimate of the transition from fluvial to debris‐flow dominated channel processes. Values of normalized hypsometry, hypsometric integral, and mean slope vs elevation are used for 14 tributary basins and the Cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration. Results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the Cullasaja basin and adjacent hillslopes. Metrics of topography (relief, slope gradient) and hillslope activity (landslide frequency) exhibit significant downstream increases below the current position of major knickpoints. The transient effect of knickpoint‐driven channel incision on basin hillslopes is captured by measuring the relief, mean slope steepness, and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the Cullasaja River. A conceptual model of area–elevation and slope distributions is presented that may be representative of post‐orogenic landscape evolution in analogous geologic settings. Importantly, the model explains how knickpoint migration and channel–hillslope coupling is an important factor in tectonically‐inactive (i.e. post‐orogenic) orogens for the maintenance of significant relief, steep slopes, and weathering‐limited hillslopes. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
928.
对雅砻江流域某拟建电站库区边坡失稳后的滑速和涌浪高度进行计算。计算滑速采用潘家铮条分法,涌浪高度计算同时采用水科院经验公式法和潘家铮法两种方法。综合两种方法的计算结果获得库坝处滑坡产生的涌浪高度为0.41~0.88m,对拟建工程影响较小。此计算分析方法对类似工程具有借鉴意义。 相似文献
929.
A new gravimetric geoid model for Sudan using the KTH method 总被引:2,自引:0,他引:2
930.
Efforts are made to enhance the predictive formula for the inception of wave breaking. To achieve success, the existing formulas are extensively reviewed. They are categorized into four types, i.e., the McCowan type, the Miche type, the Goda type and the Munk type. The inherent relations among the different types are then exploited. The differences among each formula within a group are also discussed. Four representative formulas from the different types are chosen to compare with the measured data for a total number of 1193 cases reported in literatures. It is shown that Goda's and Ostendorf and Madsen's formulas are advantageous in general among the selected ones. Goda's formula, however, is found to be inaccurate as the beach slope becomes steeper than 1/10. Ostendorf and Madsen's formula is fairly good even for cases of very steep slopes, but its accuracy for the cases of ordinary slopes is not as good as Goda's. A new predictive formula for the inception of wave breaking is proposed. The unique index, defined by ψ′b = (1.21 − 3.30λb)(1.48 − 0.54γb)ψb, where ψb = gHb/Cb2, Hb is the breaking wave height, Cb is the breaking wave celerity, λb is the breaking wave steepness, γb is the relative breaking wave height, and g is the gravity acceleration, is introduced. The incipient condition of wave breaking is then given by ψ′b = 0.69. This formula is a significant improvement to the existing ones in terms of the accuracy. In addition, it is a local relation. Further verification shows that the proposed formula performs similarly well when applied to the field and to the waves over permeable bed. 相似文献